Depletion of stratospheric Ozone Urban Air pollution Acid Deposition Depletion of stratospheric Ozone Urban Air pollution Acid Deposition

Starter – Guess the composition LO: Explain formation of air pollutants and their impact The pie chart shows below shows the composition of the gases that make up the Earth’s atmosphere. Add the following labels to your pie chart: Argon and other gases, Nitrogen, Oxygen,

The early atmosphere As the pie chart shows, the atmosphere was not always like it is now. The early atmosphere was mainly carbon dioxide and Nitrogen. This is very similar to what the atmosphere on Venus and Mars is currently like. LO: Explain formation of air pollutants and their impact

Changes in the Earth’s atmosphere The early Earth was a violent place covered in volcanoes. These released large amounts of carbon dioxide, water vapour and nitrogen into the atmosphere. LO: Explain formation of air pollutants and their impact

Changes in the Earth’s atmosphere As the Earth cooled, the water vapour condensed and fell as rain. This formed the first oceans. Comets also brought ice to the Earth, which melted and added to the water supplies. LO: Explain formation of air pollutants and their impact

Changes in the Earth’s atmosphere As the Earth began to stabilise, the early atmosphere was mainly carbon dioxide, with some water vapour and nitrogen. There was little or no oxygen as there is today. LO: Explain formation of air pollutants and their impact

Changes in the Earth’s atmosphere After the first, violent changes, the atmosphere remained relatively stable. When life appeared on Earth, it changed again. The first life was mainly bacteria and later plants. These used the carbon dioxide in the atmosphere to do photosynthesis and made oxygen in the process. Over time, this lead to the atmosphere that we know now. LO: Explain formation of air pollutants and their impact

What does this graph tell us about the atmosphere and temperature? Why is this important? What does this graph tell us about the atmosphere and temperature? Why is this important?

Structure of the Atmosphere LO: Explain formation of air pollutants and their impact Layers within the atmosphere (from the ground up) and their characteristics Troposphere km thick; 75% of all gases in atmosphere; all weather happens here; temperature falls with altitude Stratosphere km thick temperature increases with altitude (gets warmer!) horizontal winds (jet stream) contains ozone layer

Structure of the Atmosphere LO: Explain formation of air pollutants and their impact Mesosphere km thick temperature falls with altitude meteor showers happen here Thermosphere - aurora borealis and aurora australis ionosphere here (reflects radio waves for communications) can be very very hot (2000 C+) ! Exosphere - outermost layer of earth’s atmosphere 550km+ above earth’s surface satellites orbit here

Structure of the Atmosphere LO: Explain formation of air pollutants and their impact

Ozone LO: Explain formation of air pollutants and their impact

O zone is an allotrope of oxygen gas. It is made naturally in the atmosphere It can also be made by photocopiers and laser printers. Recap: What is Ozone?

Ozone Formation In the Stratosphere; Oxygen gas molecules are bombarded by high energy UV light from the Sun. This causes them to break up to form Oxygen radicals, O. UV

Ozone Formation The oxygen radicals, O., then react with more oxygen gas molecules making ozone. O 2  2O. 2O. + 2O 2  2O 3 3O 2  2O 3

Ozone Destruction The Ozone gas molecules are hit by other UV radiation from the Sun. They break up to form oxygen gas molecules and oxygen radicals 2O 3  2O. + 2O 2 UV

Ozone Destruction Oxygen radicals join up to form O 2 molecules. 2O.  O 2 2O 3  3O 2

UV The Ozone Cycle UV

Role of Ozone in absoprtion of UV radiation LO: Explain formation of air pollutants and their impact Allows UVa and UVb through, but blocks UVc waves UVa - causes wrinkles UVb - causes skin cancer UVc - worst one because of damage to organisms / tissues The energy provided by incoming UV light changes O2 → 3

What are HOG’s? LO: Explain formation of air pollutants and their impact HOG’s are usually stable but break down into halogen atoms (F, Cl, Br, I, At) which are highly reactive (CFC = chlorofluorocarbon; Cl and F are halogens; organic = contains carbon, therefore CFC = halogenated organic compound)

Ozone Depletion LO: Explain formation of air pollutants and their impact UV radiation breaks off a chlorine atom from a CFC molecule. The chlorine atom attacks an ozone molecule (O 3 ), breaking it apart and destroying the ozone. The result is an ordinary oxygen molecule (O 2 ) and a chlorine monoxide molecule (ClO). The chlorine monoxide molecule (ClO) is attacked by a free oxygen atom releasing the chlorine atom and forming an ordinary oxygen molecule (O 2 ).

Ozone depletion LO: Explain formation of air pollutants and their impact The chlorine atom is now free to attack and destroy another ozone molecule (O 3 ). One chlorine atom can repeat this destructive cycle thousands of times. Sources of HOG’s - fire extinguishers, refrigerators, AC units

Effects of UV radiation LO: Explain formation of air pollutants and their impact Reacts with melanin in skin to cause sunburn & skin cancer Overexposure degrades immune system (but how?) Required for production of vitamin D (a good thing) Interferes with photosynthesis in producers (esp. phytoplankton) Zooplankton then gain less energy from phytoplankton, and food chain suffers (i.e. productivity decreases)

Reduce LO: Explain formation of air pollutants and their impact Replace gas-blown plastics because… Replace CFC’s with CO 2, propane, or air Replace aerosol propellants Replace methylbromide pesticides with something other than GHG’s don’t use aerosol hair products or deodorant - use alternatives (gel, mousse, roll-ons etc)

Regulate LO: Explain formation of air pollutants and their impact Recover and recycle CFC’s from refrigerators and AC units HCFC’s are better because they don’t persist as long in the atmosphere; however, they are still harmful to the ozone layer (just less so than CFC’s) Legislate to have refrigerators returned to the manufacturer in order to recover materials used in building them Capture CFC’s from scrap cars AC units

Restore LO: Explain formation of air pollutants and their impact Remove chlorine from the stratosphere or add ozone (not exactly feasible!) Ozone layer is slowly replenishing itself as long as we continue the ban (see next slide

UNEP LO: Explain formation of air pollutants and their impact UNEP (United Nations Environment Programme) forges agreements on: ITIHC (International Trade in Harmful Chemicals) air pollution contamination of international waterways provide information to countries and public on disadvantages of pollution

Montreal Protocol, 1987 LO: Explain formation of air pollutants and their impact International agreement on the emission of ozone- depleting substances Froze production and consumption of CFC’s with goal of zero production by year 2000 LEDC’s granted a longer time to implement the treaty

Montreal Protocol, 1987 LO: Explain formation of air pollutants and their impact China and India have not met their quotas under the MP because of their rapid economic growth and high demand for refrigeration & AC’s good example of a successful international cooperative effort to alter human impact on the environment